In the field of vehicle drivetrain components, a transfer case is an apparatus that distributes driving power to more than one driven axle of the vehicle. A typical transfer case receives driving power from the transmission of the vehicle and transfers that power to a primary output shaft and a secondary output shaft, with the secondary output shaft being driven selectively using a clutch. In addition, two speed transfer cases provide gear reduction to allow operation in a high range, which is typically a 1:1 drive ratio, or a low range, such as a 2:1 drive ratio.
Many of the components in a transfer case require lubrication. One transfer case design includes a pump that is mounted on one of the input shaft or the primary output shaft. The pump delivers lubricant to the various components of the transfer case through an axial bore that is formed through the input shaft and/or the output shaft. Supply ports are formed through the input shaft and/or the output shaft at locations where lubrication is needed, such that the lubricant flows from the pump, through the axial bore, and out of the supply ports. This arrangement is effective but offers little control over the rate of lubricant flow to specific components.